#include<bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i=0; i<(n); i++)
#define rep2(i,l,r) for(int i=(l); i<(r); i++)
#define all(x) x.begin(),x.end()
using ll=long long;
ll LINF=(1LL<<61)-1;
ll MINF=1LL<<40;
int INF=INT_MAX>>1;
template<class S>
void out_vector(vector<S> v){
for(S i:v)cerr<<i<<" ";
cerr<<"\n";
}
#include "highway.h"
void find_pair(int N, std::vector<int> U, std::vector<int> V, int A, int B) {
int M=U.size();
ll dist=ask(vector<int>(M,0))/A;
int ok=0,ng=M;
while(ng-ok>1){
int mid=(ok+ng)/2;
vector<int> ques(M,0);
rep2(i,ok,mid)ques[i]=1;
if(ask(ques)==dist*A){
ok=mid;
}
else{
ng=mid;
}
}
vector<vector<pair<int,int>>> tree(N);
rep(i,N){
if(i!=ok){
tree[U[i]].emplace_back(V[i],i);
tree[V[i]].emplace_back(U[i],i);
}
}
int curs=U[ok],curt=V[ok];
vector<int> sdis(N,-1);
vector<int> par(N,-1);
vector<int> which(N,-1);
sdis[curs]=0;
sdis[curt]=0;
int sad;
{
stack<int> vert;
vert.push(curt);
vert.push(curs);
vector<int> ques(M,0);
int flg=1;
while(!vert.empty()){
int pos=vert.top();
if(pos==curt)flg=0;
which[pos]=flg;
vert.pop();
for(auto &[t,i]:tree[pos]){
if(sdis[t]==-1){
ques[i]=flg;
par[t]=i;
sdis[t]=sdis[pos]+1;
vert.push(t);
}
}
}
sad=(ask(ques)-dist*A)/(B-A);
vector<int> kouho;
rep(i,N){
if(which[i]==1&&sad==sdis[i]){
kouho.emplace_back(i);
}
}
ok=0,ng=kouho.size();
while(ng-ok>1){
int mid=(ok+ng)/2;
vector<int> ques(M,0);
rep2(i,ok,mid)ques[par[kouho[i]]]=1;
if(ask(ques)==dist*A){
ok=mid;
}
else{
ng=mid;
}
}
curs=kouho[ok];
}
{
sad=dist-1-sad;
vector<int> kouho;
rep(i,N){
if(which[i]==0&&sad==sdis[i]){
kouho.emplace_back(i);
}
}
ok=0,ng=kouho.size();
while(ng-ok>1){
int mid=(ok+ng)/2;
vector<int> ques(M,0);
rep2(i,ok,mid)ques[par[kouho[i]]]=1;
if(ask(ques)==dist*A){
ok=mid;
}
else{
ng=mid;
}
}
curt=kouho[ok];
}
answer(curs,curt);
}
